Wind power generator and bearing structure therefor

ABSTRACT

The invention relates to a wind power current generator comprising a bearing, a tubular stator that carries a race of the bearing, a tubular rotor coaxial with the tubular stator that can rotate in relation to the stator, a hub connected to the rotor, and at least two blades radially extending away from the hub. According to the invention, the stator and the rotor are formed with substantially tubular cross sections and are concentric to one another. The opposing surfaces of the rotor and stator carry permanent magnets and windings. The stator and rotor extend beyond either side of the magnets and the windings in order to accommodate an antifriction bearing on at least one side. The tubular nature of the rotor and stator allows easy passage of workers within the generator for maintenance thereof and of the blades. Additionally, the tubular nature facilitates air flow through the structure and out the blades, cooling equipment within the structure and aiding de-icing of the blades.

PRIORITY

This application claims priority to U.S. application Ser. No. 11/735,249which claims priority to U.S. application Ser. No. 10/489,726, itself aNational Stage application of International Patent Application No.PCT/IB2002/03741, filed 9 Sep. 2002 and claiming priority to ItalianPatent Application No. BZ2001A000043, this instant application being aDivisional Application thereof, claims the benefit of the filing dateand priority date thereof, and hereby incorporates the disclosuresthereof by reference.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of application Ser. No. 11/735,249,which is a Divisional of application Ser. No. 10/489,726 (now U.S. Pat.No. 7,205,678) and is related to U.S. patent application Ser. No.11/735,270, also a Divisional of application Ser. No. 10/489,726, thedisclosures of which are hereby incorporated by reference.

BACKGROUND AND SUMMARY

The present invention relates to a wind power generator. Moreparticularly, embodiments relate to a large-scale wind powered machinethat accommodates humans within the workings for easy access andmaintenance while providing efficient cooling of components and/orde-icing of blades. Embodiments are particularly suited to electricalpower generation via wind power.

Wind powered machines, particularly large scale electrical generators,include blades mounted on a hub attached to a rotor that rotates whenwind passes over the blades. The rotation of the rotor is then used todrive machinery, such as pumps or electrical generators. In the case ofelectrical generators, the rotor will typically carry conductorwindings/coils or magnetic field generators that face magnetic fieldgenerators or conductor windings/coils, respectively, on a stator suchthat there is relative motion between the coils and the magnetic fieldgenerators, producing electricity. The magnetic field generators aretypically field windings that are electromagnets powered by theelectrical generator once it begins producing electricity, but thatrequire electricity from a battery or the like before the electricalgenerator produces electricity.

Large scale wind powered electrical generators are becoming more common,particularly in onshore and offshore wind farm applications. In suchlarge scale generators, a tower supports a nacelle housing the stator,which supports the rotor, which supports the hub and blades. Equipmentrequired for controlling the generator, including controls for theblades and other machinery, can be housed in the tower, the nacelle,and/or in cavities within the stator and/or the rotor.

An example of a large scale wind powered generator is seen ininternational application WO 01/29413 by Torres Martinez (equivalent toEuropean Patent Application No. EP 1319830 A1) and entitled, “MultipolarAerogenerator.” So-called multipolar wind power generators typicallycomprise a wind-driven rotor associated with a power generator housed ina nacelle atop a support tower. The nacelle is mounted for rotation onthe upper end of the tower and houses electrical power generationcomponents as well as equipment for controlling the generation ofelectricity, the orientation of the nacelle, the pitch of the blades,the speed of the rotor, and more. The nacelle is rotated to position theblades of the generator for maximum exposure to wind, and the pitch ofthe blades is similarly adjusted to optimize power generation. The rotoris secured to a rotor shaft supported by two bearings in the nacelle.The bearings are in turn supported by the housing of the nacelle, whichincludes the stator of the power generator. The rotor itself iscomprised of a ring supported by a plurality of spokes extendingradially from the shaft. The ring carries electromagnets in the form offield windings on its outer surface and facing coils mounted on theinner surface of the housing of the nacelle. Wind drives the blades,which drive the rotor shaft, which rotates the rotor and moves theelectromagnetic field windings relative to the coils, generatingelectricity.

In such a multipolar generator, the structure of the rotor shaft and thesupports in the nacelle, there is no passageway between the interior ofthe tower and the interior of the blades extending away from the rotorhub. Therefore, it is difficult to reach the hub for maintenance, suchas to maintain blade pitch altering machinery, not to mention the rotoritself. Additionally, internal ventilation of the rotor blades,particularly for de-icing the blades, is difficult to accomplish. Theconstruction of the wind power generator of the type disclosed by TorresMartinez is complex with regard to the support of the rotor within thestator body.

Another multipolar synchronous generator, particularly suited forhorizontal axis wind power plants, is described in German patentspecification DE 44 02 184 by Klinger. Klinger discloses a generatorthat overcomes some of the disadvantages of the type of generatordisclosed by Torres Martinez by using a generator formed by one singlestructural unit. The single structural unit comprises a stator mountedatop a support tower, the stator being somewhat equivalent to thenacelle of Torres Martinez. The stator supports the rotor, which carriesa hub to which blades are attached. As in Torres Martinez, the statorcan rotate relative to the support tower to orient the blades formaximum wind exposure. The rotor is connected to the stator by afloating support provided within the generator, specifically, bearingsarranged between the stator and the rotor. This single structural unitsupports the rotary movement of the rotor and receives the externallyintroduced forces and torques. In the generator of Klinger, while therotor shaft and related structures and components are eliminated, thestructure of the rotor proves to be very complex, since the two surfacesof the rotor and of the stator lie at a considerable distance from theantifriction bearings of the rotor.

Therefore, embodiments avoid the shortcomings of conventional wind powergenerators by providing a wind power generator with a simpler structurein which a maximum of ventilation possibilities is guaranteed forcooling and/or de-icing. In addition, embodiments afford a large degreeof accessibility to the various components of the generator whileproviding a high level of structural stiffness.

In a preferred embodiment, the wind power generator is a multipolar,gearless, synchronous generator that is largely hollow by virtue of theuse of coaxial tubular stator and rotor elements. For additionalsimplification, embodiments employ, permanent magnets on one of statorand rotor, and windings/coils on the other of stator and rotor. Thetubular rotor element serves simultaneously as a shaft that can besupported by bearings and as a structure for anchoring magnet bodies,eliminating the need for a ring supported by spokes extending radiallyfrom a rotor. The tubular rotor element is mounted coaxially with thetubular stator element, which is connected to the supporting structure,such as a tower.

The generator of embodiments is the integrating component of thesupporting structure, and the loads are transferred directly from thehub onto the rotor shaft of the generator. The tubular rotor elementtransfers the loads into the tubular stator body by way of two bearingsdisposed at the beginning and at the end of the electrical machine.

The largely hollow structure of embodiments provides several advantagesover the structures of the prior art. For example, housing electricaland electronic subsystems inside the nacelle affords excellentprotection from lightning since the structure employs the principle ofthe Faraday cage. In addition, because the tubular structure isconfigured to accommodate the passage of adult humans, it permits easyaccess to the front portion of the nacelle and to the hub, whichfacilitates maintenance and repair work on other subsystems of the windpower generator. This also allows one to mount the hub from the inside.

The substantially hollow structure also facilitates use of the heatgiven off by equipment, such as power electronics, housed in the tower,as well as heat released by the generator itself The heat can promotethe chimney effect to guide warm air into the hub and from there intoand through the rotor blades. The warm air can thus be used as aparticularly efficient de-icing system in cooler times of the year, andprovides a cooling effect for equipment in the generator as cooler airis drawn into and passes through the hollow structure. No externalenergy needs to be supplied during operation to heat the rotor blades.Thus, the heat given off by the generator and by the power electronicsthemselves is put to use in a simple fashion.

Additional cooling benefits are derived from the hollow structure sincethe components that produce heat are moved to the periphery of thegenerator. More specifically, the generator of embodiments places thewindings on the inner periphery of the generator housing. Heat producedby the windings during electricity generation is easily conducted to theouter surface of the generator. By adding cooling fins on the outersurface according to embodiments, the heat can be transferred from thegenerator to the air stream passing over the generator duringelectricity production. The cooling fins preferably project transverselyfrom the outer surface and are substantially equally spaced apart. Whilethe fins extend longitudinally along the outer surface, they can alsohave a sweep or profile that takes into account disturbances in the airstream introduced by motion of the blades and/or the fins themselves toenhance effectiveness.

In embodiments, the substantially hollow and multipolar synchronousgenerator has permanent magnets on an outer body and has windings/coilson an interior body. This yields a machine having a stator unit on theinside and a rotor on the outside. The magnets are preferably attachedto the inner surface of the rotor in this arrangement, and the windingsto the outer surface of the rotor shaft. The advantages of such asolution are a greater specific output, the possibility of using thetotal heat released by the generator for the de-icing system, and asimplification of the positioning of the power cables required toconduct the electric current from the generator to the tower.

In other embodiments, a portion of the stator possesses a bell-likeshape, narrowing in the direction of the hub to a head with a centric,circular orifice. The rotor also possesses a bell-like shape extendingconcentrically within the bell-like portion of the stator to a head witha corresponding centric orifice which merges into a tubular boss. Thetubular boss extends through the orifice of the stator bell head,providing support for an antifriction bearing and, with its outerperiphery, the hub. Preferably, the antifriction bearing is a taperedroller bearing with a double race. The rotor in embodiments canadditionally be equipped with a brake bearing structure and can includea locking brake on the end of the rotor or stator that faces thesupporting frame. In embodiments with such braking structures, the rearbearing is omitted to accommodate the braking structure, and the frontbearing is a single special bearing, such as a tapered roller bearingwith a double race, preferably of a smaller diameter than those used indual-bearing embodiments. The single bearing is preferably mounted inthe narrowed portion in the front part of the stator structure. Thisnarrowed portion is provided in the form of a reinforcing, sandwich-liketoroidal element which only partially reduces the accessibility to thehub.

The use of a single tapered roller bearing with a double race offersseveral advantages over embodiments with two bearings. The singlebearing arrangement provides simplification of the generator mountingstructure since only one-side need accommodate a bearing. The singlebearing arrangement eliminates hazardous eddy currents in the generatorthat form temporary circuits between the stator wall, the rotor wall,and roller bodies of the bearings disposed at the ends of the activeportion (windings/coils) of the two bearing arrangement. Further, thesingle bearing arrangement simplifies adjustment processes of thebearing since the tapered rollers must be pre-stressed; embodiments withtwo bearings at the ends of the generator present design problems withrespect to the construction tolerances and thermal deformation. Thesingle bearing arrangement requires only one system of seals andlubrication concentrated in the front region of the generator. And thebearing typology used in the single bearing arrangement offers a highdegree of rolling precision since pre-stressing the rollerssubstantially eliminates play in the bearing, as well as providing a lowrolling resistance that increases generator productivity and efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional features and details are contained in the claims and in thedescription of a power generator actuated by wind, in its preferredembodiments as illustrated in the accompanying drawings, in which:

FIG. 1 shows a sectional view along a vertical axial plane of a powergenerator actuated by wind energy, in accordance with embodiments havingthe rotor tubular section within the stator tubular section;

FIG. 2 shows a power generator according to embodiments in a sectionalview like that of FIG. 1, but with the stator tubular section within therotor tubular section.

FIG. 3 shows a power generator according to embodiments in which therotor tubular section is within the stator tubular section and a singlebearing is employed.

DESCRIPTION

In FIG. 1 a wind power generator is generally indicated by the referencenumber 1. This generator is mounted by way of a hollow transitionelement 2 to the upper. end of a tower not further illustrated. The windpower generator 1 comprises a stator 3 and a rotor 4. The rotor 4 isconnected in a known manner to a hub 5, to which, in the present case,three hollow blades not shown here are connected. The blades areattached to flanges 6 of the hub 5. The rotor 4 is has a substantiallytubular cross section and, in the example shown in FIG. 1, permanentmagnets 7 are set in the outer surface of the rotor 4. These magnets 7are arranged opposite windings 8 secured on the inner surface of a thestator 3, which also has a substantially tubular cross section.Antifriction bearings 9, 10 are arranged in the end regions of thetubular stator 3. These bearings 9, 10 cooperate with the stator 3 torotatably support the tubular rotor 4. Of the two antifriction bearings9, 10, at least one must at least include a thrust bearing portion. Bothbearings 9, 10 are arranged in such a manner that the permanent magnets7 and the windings 8 are between the bearings 9, 10 in a direction alongthe rotational axis of the rotor 4. It should be noted that whilepermanent magnets 7 are preferred, they could be replaced by fieldwindings, though this yields a more complicated structure.

The hub 5 is attached by its flange 11 to one of the ends of the tubularrotor 4. For example, in embodiments, the flange 11 is joined bythreaded bolts 13 to an annular collar 12 of the tubular rotor 4.

On the side facing the hub 5, the tubular rotor 4 preferably has adepression 14 in its outer surface, which can receive the inner ring 15of the antifriction bearing 9, while the outer ring 16 of the samebearing 9 is mounted on the inner surface of the tubular stator 3. Inaddition, the antifriction bearing 9 is preferably held in thedepression 14 by an angular ring element 17.

On the end facing away from the hub 5, the tubular stator 3 is connectedin embodiments to a flange 19 of the transition element 2, which flangeis joined, for example, by screws 21 to a thickened edge 20 in thetubular stator 3. The outer ring 22 in the antifriction bearing 10 ispreferably held in position by a radial land 23 of the stator 3 and by aspacer 18 directly abutting the flange 19, while the inner ring 24 ofthe same antifriction bearing 10 is received on a belt 25 recessed intothe outer surface of the tubular rotor 4. The inner ring 24 can furtherbe held in position by an angular element 26 with an L-shaped crosssection.

The stator 3 need not be the outer member in all embodiments. Forexample, as seen in FIG. 2, a wind power generator 100 can comprise asubstantially tubular rotor 104 located on the outside of asubstantially tubular stator 103. The rotor 104 is supported by thestator 103 via bearings in a manner similar to that described withreference to FIG. 1. In this case, the windings 108 are preferablylocated on the outer surface of the stator 103, while the permanentmagnets 107 are mounted on the inner surface of the rotor 104. Again,while permanent magnets 107 are preferred, they could be replaced byanother type of magnetic field generator, such as field windings, thoughthis yields a more complicated structure.

In a preferred embodiment shown FIG. 3, the wind power generator 200 isaffixed to a frame 201 on the upper end of a tower 202 that is onlypartially shown. In this case as well, the wind power generator 200 hasa stator formed with a substantially tubular cross section 203. One endof the tubular stator 203 is fastened, such as by a screw connection204, to the frame 201. While the stator is shown on the outside aspreferred, it should be apparent that the rotor could be on the outsidein a fashion similar to the arrangement of FIG. 2.

Radial cooling fins 205 extend from the outer surface of the outsidemember, preferably in substantially equally spaced apart relationship toone another. The fins 205 can extend parallel to the longitudinal axisof the stator 203, but could also have a profile taking into accountdisturbances in the air stream induced by motion of the blades and/orthe fins 205 themselves. Preferably, the fins 205 project transverselyfrom the outer surface. In FIG. 3, in which the tubular stator 203 isthe outer member, the radial cooling fins 205 extend from the outersurface of the tubular stator 203, while stator windings 206 are mountedon the inside surface of the tubular stator 203. On the end of thetubular stator 203 facing away from the screw connection 204, thewindward end of the stator 203, the stator 203 possesses a bell-shapedextension that narrows toward the hub of the generator, ending in atorus-shaped, sandwich-like head 207 with a central orifice. This head207 supports on an inner surface of its orifice an outer ring 208 of abearing 210, preferably a tapered roller bearing. The tubular rotor 213has a corresponding, coaxial bell-shaped extension narrowing within thestator 203 to its own head/toroidal bottom 212 with its own centralorifice that forms a tubular boss 211 within the central orifice of thestator 203. The tubular boss 211 carries an inner ring 209 of thebearing 210 so that the boss 211 is supported by the stator 203 inconjunction with the outer ring 208 of the bearing. The tubular rotor213 preferably carries permanent magnets 214 its outer surface such thatthe magnets 214 lie opposite the windings 206 on the substantiallytubular stator 203. It should be noted that, as with the embodimentsshown in FIGS. 1 and 2, the preferred permanent magnets 214 could bereplaced with field windings, but that the permanent magnets 214 affordat least the advantage of not requiring a power source to generatemagnetic fields. The substantially tubular rotor 211 is preferablyconnected to a hub 216 by, for example, a screw connection 215 having acovering or hood 217.

On the side facing away from the tubular boss 211, the leeward end ofthe tubular rotor 213, the rotor 213 is preferably oriented toward abrake supporting structure 218, which can brake the tubular rotor 213,thereby slowing or stopping the rotational motion of the blades.

It will be appreciated that various of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Also, itshould be noted that various presently unforeseen or unanticipatedalternatives, modifications, variations or improvements therein may besubsequently made by those skilled in the art which are also intended tobe encompassed by the following claims.

1. A wind power generator connectable to a support structure and comprising: a hollow tubular stator without a drive shaft structure to form a passage for maintenance; a hollow rotor mounted coaxially outside the stator; a plurality of magnetic field generators including permanent magnets mounted on the rotor; a plurality of windings mounted on the stator and facing the magnetic field generators; and a plurality of radially projecting spaced apart cooling fins coupled to an external surface of the rotor such that heat produced by the windings is conducted to the cooling fins, the heat being removed from the cooling fins by air passing around the wind power generator.
 2. The wind power generator of claim 1 wherein the cooling fins project substantially transversely to the external surface of the rotor.
 3. A wind power generator connectable to a support structure and comprising: a hollow stator; a hollow tubular rotor mounted coaxially inside the stator and without a drive shaft structure to form a passage for maintenance; a plurality of magnetic field generators including permanent magnets mounted on the rotor; a plurality of windings mounted on the stator and facing the magnetic field generators; and a plurality of radially projecting spaced apart cooling fins coupled to an external surface of the stator such that heat produced by the windings is conducted to the cooling fins, the heat being removed from the cooling fins by air passing around the wind power generator.
 4. The wind power generator of claim 3 wherein the cooling fins project substantially transversely to the external surface of the stator.
 5. The wind power generator of claim 3 wherein the radial cooling fins extend from the outer surface of the stator in a substantially equally spaced apart relationship to one another.
 6. The wind power generator of claim 3 wherein the fins extend parallel to the longitudinal axis of the stator.
 7. A wind power generator connectable to a support structure, said wind power generator comprising: a hollow stator; a bearing supported by the stator; a hollow tubular rotor mounted inside the stator and supported by the bearing so that the rotor can rotate relative to the stator and is coaxial with the stator and is without a drive shaft structure to form a passage for maintenance; a plurality of magnetic field generators including permanent magnets mounted on the rotor; a plurality of windings mounted on the stator and facing the magnetic field generators; and a plurality of radially projecting spaced apart cooling fins coupled to an external surface of the stator such that heat produced by the windings is conducted to the cooling fins, the heat being removed from the cooling fins by air passing around the wind power generator. 